Electrical testing apparatus



A ril 11, 1939. c. PAULSON 2,153,990

ELECTRICAL TESTIN APPARATUS Filed 001;. 15, 1937 'm/vs/vro/e' C. PA ULSON A OR/YE Y Patented Apr. 11, 1939 UNITED STATES PATENT OFFICE Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application October 15,

4 Claims.

This invention relates to electrical testing apparatus and more particularly to a device for determining whether a piece of electrical apparatus has certain electrical characteristics.

It is an object of the present invention to provide an apparatus for rapidly making a test for determining whether or not an article has predetermined electrical characteristics.

In accordance with one embodiment of the invention, an apparatus is provided for determining whether an electrical coil has a resistance within predetermined desirable limits. In the preferred embodiment of the invention, a coil is moved to a position where its terminals complete a Wheatstone bridge circuit, and in so moving, the coil mechanically actuates a pair of contacts to initiate the operation of a series of relays and connect a meter type relay across the bridge circuit whereby a high and low limit test 20 are made automatically and an audible signal given if the coil under test is within the predetermined limits solely by the insertion of the coil into the apparatus.

A better understanding of the invention may be 25 had by reference to the following detailed description of the preferred embodiment of the invention when considered in conjunction with the accompanying drawing, wherein a single schematic view shows diagrammatically the features thereof.

In the drawing, the reference numeral l designates a coil which is to be tested and which may be moved into a position to engage its terminals II and I2 with a pair of contacts l3 and I4 of a bridge circuit, indicated generally by the numeral IS. The coil It], in being moved to position to engage its terminals II and I2 with the contacts 3 and I4, will pass through a suitable .ilg l6 having a slot ll therein in which is pivoted a lever l8 for closing a pair of contacts I9 upon the insertion of the coil I0 into the fixture l6 and into engagement with the contacts l3 and I4. The contacts l3 and I4 are so positioned with respect to the lever l8 that contacts l3 and 4 are in engagement with terminals II and I2 before lever I8 closes contact IS.

A main switch 25 is provided for placing the apparatus in condition for operation. This switch 25 is adapted, upon closure thereof, to connect grounded battery at 26 to one side of the windings of each of a series of relays 21, 28, 29, 30, 3| and 32, to one side of the winding of a solenoid 33, and to one side of the winding of a buzzer 34.

The solenoid 33 forms part of a meter type 1937, Serial No. 169,177

relay 40, the parts of which are shown enclosed in dotted lines. This relay includes a galvanometer type movable coil 4| having fixed thereto a contactor 42 which will be rocked about a coil pivot 43 in either of two directions, depending upon the direction of unbalance of the bridge circuit l5. The contactor 42 is normally held in its midposition by a pair of levers 45 and 46, pivoted at 41 and 48, and connected to the movable element of the solenoid 33 by a pair of links 49 and 50, respectively. The contacto 42 is adapted, upon movement thereof by the movable coil 4|, in a clockwise direction to engage a fixed contact 55 connected to ground at 56, and upon movement thereof in a counter-clockwise direction by the moving coil 4| to engage a fixed contact 5'! connected to a fixed contact 58 of a relay 59. One side of the winding of the relay 59 is connected to its back contact 60 and to grounded battery through the winding of the relay 29. The moving coil 4| has one end of its winding connected to a point 65 on the bridge l5 and its other end is connected to a fixed contact 66 of relay 30.

The bridge circuit I5 has a battery 61 connected thereacross between the points 68 and 69, and in the arm thereof, between the points 65 and 69, has a variable resistance 10, the value of which may be adjusted to the value desired in the coil ID to be tested. The coil l0, upon its insertion in the fixture I6, will be connected across an arm of the bridge I 5 between the point 69 and a point II. The other arms of the bridge circuit, that is, the arms between the points 68 and II and between the points 65 and 68, have a resistance 12 and a pair of resistances l3 and 14, respectively, connected thereacross. The resistance 12 may be of any suitable value comparable with the value of the resistances l3 and 14 combined. For example, the resistance 12 may be 500 ohms and the resistances l3 and 14 may have a value of and 475 ohms resistance, respectively, and the resistance 13 is so connected that upon energization of the relay 28, it will be cut out of the bridge circuit I5. 45 This is accomplished by connecting the point of the bridge circuit to a fixed contact 16 of the relay 28 and connecting a movable contact 'l'l associated with the contact 16 to a point on the bridge circuit between resistances l3 and 14.

The insertion of a coil Ill into the fixture l6, as pointed out hereinbefore, will effect the closure of the pair of contacts l9. This will initiate the operation of the circuit by connecting ground at to one side of the relay 21, the other side 5 of the winding of which had been connected to grounded battery at 28 through the closureot the switch 25. The relay 21 is a retarded relay and will pull up somewhat slowly to prepare a circuit for operating relay 58 by connecting ground at 8| through make contact 3| of relay 2! to a front contact 82 of relay 2! and will complete a circuit to operate the relay 38 by connecting ground at 33 through make contact 85 to one side of the winding of the relay 38. The relay 38, upon operation, connects ground at 33 through its make contact 33 to the winding of relay 3|, and relay 38, which is also a retarded relay, will connect the moving coil 4| to the bridge circuit through its fixed contact 88 and a movable contact 83 associated therewith. The energization of relay 3| over the circuit Just traced will cause it to attract its break make contact 82 to break the circuit from grounded battery at 28 through the switch 25, solenoid 33 and a resistance 83 to ground at 34. The solenoid 33, it will be noted, was energized as soon as the switch 25 was closed over a circuit from grounded battery at 28 through the winding of the solenoid and through the resistance 83 to ground at 84. The energization oi relay 3| will prepare a circuit to operate the solenoid 33 at a later time in the cycle 01! operation over a path which extends through a break contact 85 of relay 32, a make contact 85, and make before break contact 81 oi. relay 28 to ground at 98. The ground at 88 is normally connected through a break make contact 98 of relay 28 to the contactor l2, and upon energization of relay 28, the contact 83 is shifted into engagement with a contact Ill connected to one side of the winding of buzzer 34.

The relay 32 is energized by the operation of the relay 58, which will connect ground at I85 through its make contact I35 to the winding of the relay 32. The relay 58 will be operated serially with the relay 2! upon the energization of the relay 28 over the circuit from ground at 3| through contacts 84 and 32 of relays 21 and 29, respectively, through the winding of relay 58 and winding of relay 28 to grounded battery at 28. The energization of relay 28 controls the operation of relay 59 and relay 23 will operate when relay 23 operates due to the completion of the circuit from ground at I88 through contact I08 of relay 29, winding oi relay 28 to grounded battery at 28.

It is believed that a complete understanding of the purposes and operation or the hereinbetore described apparatus and circuit connections may be had from the following description of the operation thereof. The test set is placed in condition for operation upon the closure 0! the switch 25, which, as pointed out hereinbeiore, will supply grounded battery to the various relays and to the solenoid 33, and the solenoid will immediately be operated over the circuit from grounded battery at 25 through switch 25, winding of the solenoid, resistance 83, contact 82 to ground at 84, thereby moving the arms 45 and 48 upwardly to center the contactor l2 and hold it in its midposition. with the apparatus in this condition,

coil 21, the other side of the winding of which is connected to grounded battery at 28, thereby energizing the coil 21. Energization oi the coil 21 will connect ground at 33 through contact 35 and winding of the relay 33 to grounded battery at 28, energizing relay 38. When relay 38 pulls up, it will complete the circuit through the movable coil 4| by connecting the point II of the bridge I5 through the contacts 88 and 58 to one side of the winding of the coil 4|, the other side of the winding of which is connected to the point 85 of the bridge. Simultaneously, the relay 3!! will connect ground at 88 through contact 33 and the winding of the coil 3| to grounded battery at 28 to energize coil 3| and release the solenoid 33, thereby to permit the movable coil II to move contactor 32 to either the right or leit, depend ing upon the direction of current flow through movingcoil 4|,

If the resistance in the coil III is equal to or less than the permissible maximum limit, the current in the moving coil 4| will cause the contactor 22 to move into engagement with the contact 51, thereby to complete a circuit from ground at 98 through make before break contact 81, break make contact 88, contactor 42, contacts 51, 53 and 50, to one end of the winding of the coil of relay 2!, the other end of which is connected to grounded battery at 25. Thus, it the resistance of a coil under test is equal to or less than the maximum resistance, the relay 29 will be energized, and upon energization will connect ground at I88 through contact I88 to the winding of the relay 28 to energize it and will connect ground at 8| through contact 84 of energized relay 21 and contact 82 of relay 28 to the winding of relay 53. Relay 58 will thus have ground upon both ends oi its winding until solenoid 33 is operated again, at which time relay 5! will operate to complete a circuit from ground at I15 through contact I88 to operate relay 22.

In operating, over the just described circuit, relay 28 will attract contact 38 and the circuit from ground at 98 will make on contact 36 before it breaks from contact 93 to complete a circuit from ground at 98 through contacts 91 and 85 of relay 28, contact 95 of relay 32, resistance 93, winding of solenoid 33 to grounded battery at 25, thereby operating the solenoid 33. Operation of solenoid 33 causes arms 45 and 36 to restore the contactor 42 to its midposition and hold it there until the solenoid is released. Upon completely operating, the relay 28 short circuits the section of the bridge arm 55--i8, which includes the resistance 13, thereby preparing the apparatus to check the coil II for minimum resistance, the coil having been tested for its maximum resistance. The operation of the relay 28 also opens the short circuit of the winding of relay 58, permitting it to operate.

The operation of relay 58 opens the circuit to contact 51 and closes the circuit from ground at I 85 to operate relay 32 and release the solenoid 33 which had been operated. In releasing, the solenoid 33 will permit the contactor 42 to move in a direction dependent upon the direction 01' current flow in the moving coil 4|.

It the resistance of the coil I8 is equal to or greater than the permissible minimum, the current in the moving coil 4| will cause the contactor 42 to engage the contact 55. If contactor 42 engages contact 55, a circuit will be completed from ground at 58 through the contactor, con tacts 98 and ill oi. relay 28, through the winding of the buzzer 34 and switch 25 to grounded butaioaooo tery at 26, operating the buzzer. The operation of the buzzer is an indication that the coil i is within the permissible minimum and maximum resistance limits and the coil may therefore be removed from the fixture it. The removal of the coil from the fixture will permit contacts it to open, releasing relays 21, 28, 29, 30, 3i, 32 and 59 and placing the set in condition for another test, which may be initiated by inserting another coil in the fixture.

If the coil under test has "resistance greater than the maximum permissible, the circuit from ground at 98 through the relay coil 29 will not be completed and the buzzer will not operate. If, on the other hand, the coil i under test is less than the permissible minimum, the circuit will operate to the point where' relay 32 operates to release the solenoid 33, but the contactor 62 will engage contact a second time and the buzzer will fail to operate due to the break in its operating circuit at contact 58 of relay 59 now operated.

Although a specific embodiment of the invention has been described hereinbefore, it will be understood that many changes and modifications may be made in the circuit without departing from the scope of the invention, which is to be limited only by the scope of the appended claims.

What is claimed is:

1. Testing apparatus, comprising a Wheatstone bridge circuit, a meter type relay connectible across the bridge circuit, a switch operable by an article to be tested for connecting the relay across the bridge, and means for including the article in the unknown arm of the bridge circuit prior to the operation of said switch.

2. resting apparatus, comprising a Wheatston'e bridge circuit, a meter type relay connectible across the bridge circuit, means operable by an article to be tested for connecting the relay across the bridge including a switch positioned to be operated by the article in moving to a predetermined position, and circuits under control of said switch for making said connection, and means for including the article in the unknown arm of the bridge circuit prior to the connection of the relay across the bridge circuit.

3. Testing apparatus, including a Wheatstone bridge circuit, means for connecting an article to be tested in one arm of said bridge circuit, means operable by an article moving into operative association with said bridge circuit for preparing the bridge circuit to make a test, said last named means being operable after the article is connected to the bridge, means controlled by the bridge circuit for changing the value of one arm of the bridge circuit to prepare for a second test if the article meets the first test, and means for giving a signal if an article also meets the second test.

4. Testing apparatus, comprising a Wheatstone bridge circuit, a meter type relay connectible across the bridge circuit and normally disconnected from said bridge, means for connecting an article to be tested in an arm of said bridge circuit, and means operated by the article after its connection to the bridge circuit for connecting the meter type relay across the bridge circuit and simultaneously initiating testing operations.

CHRISTIAN PAULSON. 

